On board lecturers who are required to be on stage at 2 cannot, must not show up at 2.

How early? That depends on the props you are using and your need for technical assistance.

30 minutes before you start talking is not too early. In most cases the support staff will not even be there until 15-20 minutes before. And sometimes later than that.

I go early, walk the stage, sit in different seats to get an idea of what the audience is seeing from their perspective. I check the lighting. I even strike up conversations with people who seem to be just wandering, maybe looking for something to do.

I might even say things out loud to get an idea of the acoustics in case my sound doesn’t work.